Imaging and dosimetric characteristics of 67 Cu

In recent years the use of beta-emitting radiopharmaceuticals for cancer therapy has expanded rapidly following development of therapeutics for neuroendocrine tumors, prostate cancer, and other oncologic malignancies. One emerging beta-emitting radioisotope of interest for therapy is Cu-67 (t(1/2): 2.6 d) due to its chemical equivalency with the widely-established positron-emitting isotope Cu-64 (t(1/2): 12.7 h). In this work we evaluate both the imaging and dosimetric characteristics of Cu-67, as well as producing the first report of SPECT/CT imaging using Cu-67. To this end, Cu-67 was produced by photon-induced reactions on isotopically-enriched Zn-68 at the Low-Energy Accelerator Facility (LEAF) of Argonne National Laboratory, followed by bulk separation of metallic Zn-68 by sublimation and radiochemical purification by column chromatography. Gamma spectrometry was performed by efficiency-calibrated high-purity germanium (HPGe) analysis to verify absolute activity calibration and establish radionuclidic purity. Absolute activity measurements corroborated manufacturer-recommended dose-calibrator settings and no radionuclidic impurities were observed. Using the Clinical Trials Network anthropomorphic chest phantom, SPECT/CT images were acquired. Medium energy (ME) SPECT collimation was found to provide the best image quality from the primary 185 keV gamma emission of Cu-67. Reconstructed images of Cu-67 were similar in quality to images acquired using Lu-177. Recovery coefficients were calculated and compared against quantitative images of Tc-99m, Lu-177, and Cu-64 within the same anthropomorphic chest phantom. Production and clinical imaging of Cu-67 appears feasible, and future studies investigating the therapeutic efficacy of Cu-67-based radiopharmaceuticals are warranted.

Automated summary

The study evaluated the imaging and dosimetric characteristics of Cu-67, and reported the first SPECT/CT imaging using Cu-67. The production and clinical imaging of Cu-67 appeared feasible, indicating potential applications in radiopharmaceuticals for therapy.